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Combination of smoking and heavy drinking ‘speeds up cognitive decline’

11 July 2013

The combination of smoking and heavy drinking speeds up cognitive
decline, according to a new study by researchers in UCL Epidemiology & Public Health.

The research, published in the British Journal of Psychiatry, found that smokers who
drank alcohol heavily had a 36% faster cognitive decline compared to
non-smoking moderate drinkers.

Smoking and heavier alcohol consumption often co-occur, and their
combined effect on cognition may be larger than the sum of their individual
effects. The research team assessed 6,473 adults (4,635 men and 1,838 women)
aged between 45 and 69 years old over a 10-year period. The adults were part of
the Whitehall II cohort study of British civil servants.

All the participants were asked about their cigarette and alcohol
consumption, and their cognitive function (including verbal and mathematical
reasoning, short-term verbal memory and verbal fluency) was then assessed three
times over 10 years.

The team found that in current smokers who were also heavy
drinkers, cognitive decline was 36% faster than in non-smoking moderate
drinkers. This was equivalent to an age effect of 12 years – an additional two
years over the 10-year follow up period. Among smokers, cognitive decline was found
to be faster as the number of alcohol units consumed increased.

From a public health perspective, the increasing burden associated with cognitive aging could be reduced if lifestyle factors can be modified.

Dr Gareth Hagger-Johnson, UCL Epidemiology & Public Health

Lead researcher Dr Gareth Hagger-Johnson said: “Our research shows that
cognitive decline was 36% faster in those people who reported both cigarette
smoking and drinking alcohol above the recommended limits (14 units per week
for women, 21 units per week for men). When we looked at people who were
heavy-drinking smokers, we found that for every 10 years that they aged their
brains aged the equivalent of 12 years.”

Dr Hagger-Johnson went on to say: “From a public health perspective, the increasing burden associated
with cognitive aging could be reduced if lifestyle factors can be modified, and
we believe that people should not drink alcohol more heavily in the belief that
alcohol is a protective factor against cognitive decline.

"Current advice is
that smokers should stop or cut down, and people should avoid heavy alcohol
drinking. Our study suggests that people should also be advised not to combine
these two unhealthy behaviours – particularly from mid-life onwards. Healthy
behaviours in midlife may prevent cognitive decline into early old age.”